Preparation and structural characterization of O-acetyl agarose with low degree of substitution

Abstract

Among the biodegradable polymers, the polysaccharides have been found to be promising carriers for bioactive molecules. From a general standpoint, they present several reactive groups, such as hydroxyl, carboxyl and amine, that can be modified in a number of ways, giving rise to suitable devices for controlled release. In this paper, agarose was submitted to O-acetylation reactions under heterogeneous conditions, using acetic anhydride and pyridine, aiming to observe the effect of acetyl groups on the agarose properties. The products were characterized by Infrared and 1 H NMR spectroscopies. In the range of average acetylation degrees (DA) 0.07-0.48, the polymers presented partial solubility in boiling water and in common organic solvents. The 1 H NMR spectra presented evidences of non-homogeneous acetyl group distribution along the chains, as concluded from the solubility of only one of the fractions with DA<0.09, in boiling water .